From Longman Dictionary of Contemporary Englishtonicton‧ic /ˈtɒnɪk $ ˈtɑː-/ noun1[countable, uncountable] (also tonic water)DFD a clear bitter-tasting drink that you can mix with alcoholic drinks such as gin or vodkaShe sat and sipped a gin and tonic.2[countable]MD a drink that you have as a medicine to give you more energy or strength when you feel tiredA lot of people need a tonic at the end of the winter.3[countable usually singular] British EnglishHEALTHY something that makes you feel happy and full of energyA weekend by the sea was the perfect tonic.4[countable] a liquid that you put on your hair or skin to improve it and make it more healthya herbal skin tonic5[countable usually singular] technicalAPM the first note in a musicalscale of eight notes

Examples from the Corpus

tonic• It was a tonic we needed.• I'll have a gin and tonic.• He said he had drunk eight to 10 pints of lager and some vodka and tonic, the court was told.• It was good tonic for me to watch this.• There was a lot of hair tonic in evidence.• an herbaltonic• And remember, nothing - no skin tonic, astringent, freshener or plaincold water - can close your pores.• Humor was the tonic that brought Reeves out of his depression.